LEDs or Halogens?

[Russ]

I want to light up a large tray of ice from within. I was going to throw in
a bunch of 10w halogen bulbs wrapped in blue gel, but then it occurred to me
that 40-50w worth of light might melt a lot of ice.

Would high-intensity blue LEDs be a better solution - ie, do they have
better efficiency than halogens? Can anyone suggest a suitable source?

Russ.

 

[Phil Allison]

I want to light up a large tray of ice from within. I was going to throw in
a bunch of 10w halogen bulbs wrapped in blue gel, but then it occurred to me
that 40-50w worth of light might melt a lot of ice.

Would high-intensity blue LEDs be a better solution - ie, do they have
better efficiency than halogens? Can anyone suggest a suitable source?

** A 20 watt ( 18 watt ) fluoro wrapped in blue plastic gift wrap or gel.




........... Phil

 

[David L. Jones]

I want to light up a large tray of ice from within. I was going to throw in
a bunch of 10w halogen bulbs wrapped in blue gel, but then it occurred to me
that 40-50w worth of light might melt a lot of ice.

Would high-intensity blue LEDs be a better solution - ie, do they have
better efficiency than halogens? Can anyone suggest a suitable source?

Russ.

LEDs and Halogens have a similar efficiency.
Do you actually need 50W worth of light in this thing?
Some tests might be in order before you commit to a solution perhaps?

Dave

 

[Arpit]

How big?
\

 

[Russ]

As I described in another reply, the application is a large tray full of ice
(about 3ft wide and 5ft long, 3" deep) with glasses and booze for a launch.

At the moment I'm thinking of 3 x 15w pigtail-type halogen bulbs arranged
along the tray. Though I haven't had much experience with high-intensity
LEDs, having just tried one 15w halogen bulb, I can't imagine even a bunch
of LEDs coming close to it's light output.

Russ.

 

[Russ]

LEDs and Halogens have a similar efficiency.
Do you actually need 50W worth of light in this thing?
Some tests might be in order before you commit to a solution perhaps?

The application is a large tray full of ice (about 3ft wide and 5ft long, 3"
deep) with glasses and booze for a launch. The theme is winter & ice, so the
light needs a blue tint. Ideally I'd prefer to shine light in, perhaps from
each end, through a clear portal cut in the tray, but I don't have mangling
rights on the tray.

I found a 15w spare bulb for a garden light - pigtail style, not reflector.
I soldered a wire to it and hot-glued it inside a little test tube and put
it in a flask of water. The first issue I discovered is that if you have it
on before you put it in the water, the heated air inside the tube cools when
it goes in, sucking in water. I'm not too worried about getting the bulb
wet, the test tube it to protect the bulb and for ease of handling (quartz
doesn't like oily fingers).

Damn it's bright

The room will be dim - I guess I'd like an impressive emanation of light,
without risking melting the ice prematurely. For that reason I was thinking
LEDs might be more efficient, requiring a greater quantity, but with less
risk of meltdown. If the efficiency is similar, I already have a few of
these spare bulbs kicking around and a 105W transformer.

First guess would be 3 of these 15w bulbs arranged along the length.

Hmm. Maybe I'll have to break out the ice-cube trays...

Russ.

 

[Arpit]

As I described in another reply, the application is a large tray full of ice
(about 3ft wide and 5ft long, 3" deep) with glasses and booze for a launch.

At the moment I'm thinking of 3 x 15w pigtail-type halogen bulbs arranged
along the tray. Though I haven't had much experience with high-intensity
LEDs, having just tried one 15w halogen bulb, I can't imagine even a bunch
of LEDs coming close to it's light output.

Leds in your application will be more efficient. However, their light
output wont be enough.

 

[The real Andy]

Leds in your application will be more efficient. However, their light
output wont be enough.

I don't know about that man, those new Blue LED's are pretty fuggin
bright...

 

[Newsy]

throw to

The application is a large tray full of ice (about 3ft wide and 5ft long, 3"
deep) with glasses and booze for a launch. The theme is winter & ice, so the
light needs a blue tint. Ideally I'd prefer to shine light in, perhaps from
each end, through a clear portal cut in the tray, but I don't have mangling
rights on the tray.

I found a 15w spare bulb for a garden light - pigtail style, not reflector.
I soldered a wire to it and hot-glued it inside a little test tube and put
it in a flask of water. The first issue I discovered is that if you have it
on before you put it in the water, the heated air inside the tube cools when
it goes in, sucking in water. I'm not too worried about getting the bulb
wet, the test tube it to protect the bulb and for ease of handling (quartz
doesn't like oily fingers).

Damn it's bright

The room will be dim - I guess I'd like an impressive emanation of light,
without risking melting the ice prematurely. For that reason I was thinking
LEDs might be more efficient, requiring a greater quantity, but with less
risk of meltdown. If the efficiency is similar, I already have a few of
these spare bulbs kicking around and a 105W transformer.

First guess would be 3 of these 15w bulbs arranged along the length.

Hmm. Maybe I'll have to break out the ice-cube trays...

Another way of lighting up a tray would be to use electroluminescent sheet
in the bottom of the tray.

Rod

 

[Arpit]

I don't know about that man, those new Blue LED's are pretty fuggin
bright...

I mean to rival the halogens you'll need heaps. A few luxeon stars
would do the job easily though.

 

[Peter Howard]

Wot about those dopey blue decorative lights (neons I think) that half-wits
put on the outside of their cars? I've seen them in Super Crap Auto (Qld car
accessory store) but didn't pay much attention.
Or disco snake lights? They come in a clear flexible vinyl hose which will
be waterproof when you sink it in the ice.
For that matter, if you go for blue leds you could solder them up with their
dropper resistors at intervals between two lengths of hookup wire and pull
the result through suitable length of vinyl hose. If you staggered the
soldered joints to the hookup wire you probably wouldn't even need to
insulate the joints, though a bit of 3M self-amalgamating rubber tape on the
joints might make you feel better. Anyway, the plugged hose goes in the ice
and the free end snakes over the edge of the tub and thence to the power
source. You'd have to experiment to see how many leds per foot you'd want.

P

 

[Russ]

Wot about those dopey blue decorative lights (neons I think) that half-wits
put on the outside of their cars? I've seen them in Super Crap Auto (Qld car
accessory store) but didn't pay much attention.
Or disco snake lights? They come in a clear flexible vinyl hose which will
be waterproof when you sink it in the ice.
For that matter, if you go for blue leds you could solder them up with their
dropper resistors at intervals between two lengths of hookup wire and pull
the result through suitable length of vinyl hose. If you staggered the
soldered joints to the hookup wire you probably wouldn't even need to
insulate the joints, though a bit of 3M self-amalgamating rubber tape on the
joints might make you feel better. Anyway, the plugged hose goes in the ice
and the free end snakes over the edge of the tub and thence to the power
source. You'd have to experiment to see how many leds per foot you'd want.

I looked at those cold-cathode tubes that Jaycar flog for the clueless to
glue to their A-pillars and mud-flaps, but it occurred to me that they use
high-voltage supplies that may not be too compatible with water - although
your clear tubing idea might solve that concern.

As for LEDs, I get the impression (only from the bright blue ones on my
computer case) that they are highly directional - I'm not sure within a tube
I could guarantee they all point in a sensible direction - although the
refractive properties of the ice cubes might alleviate that issue.

My main concern is that I can't experiment with the actual tray until the
day of the launch. Since I have pigtail-type halogen bulbs handy, I'm going
to try a small tray of icecubes and see if they last the couple of hours
required. If not, I'll have to start considering cooler options.

Russ.

 

[John Tserkezis]

I want to light up a large tray of ice from within. I was going to throw in
a bunch of 10w halogen bulbs wrapped in blue gel, but then it occurred to me
that 40-50w worth of light might melt a lot of ice.

Thought about fibre optics? You might be able to find some cheap raw fibre
as used in those fibre optic ornamental trees (popular in the 70's). Or maybe
some sort of light pipe. Or perhaps mirrors.
It would move the heat problem to some other location where it can be managed
more effectively.

Would high-intensity blue LEDs be a better solution - ie, do they have
better efficiency than halogens? Can anyone suggest a suitable source?

Leds have a similar efficiency to halogens, so you won't have a power or heat
advantage there. It would however blow the cost right out.

 

[amstereo - matt2]

What about you get ur blue / white LED's, and drill 3mm holes in the ice
block and push the LED's in to the hole (internal illumination) seal the
leads to the LED so she don't short, and run at a low enough level to
minimise heat. when u apply the led's to the ice-block, put a SMALL amound
of salt on the injection point to lower the defrost temp in that area
temporarily to 'cement' the led's in there?

 

[David Sauer]

As I described in another reply, the application is a large tray full of ice
(about 3ft wide and 5ft long, 3" deep) with glasses and booze for a launch.

Price wise, I'd just get a twin flouro troffer light. They're normally
4ft long and 1ft wide, just get a couple of them. The kind of light
used in offices with t-bar ceilings, just mount it underneath the
tray. Comes pre-made with leads, just plug in.

Why reinvent the wheel for a simple job, if you want fancy colours,
then go buy a sheet of perspex and place over the top.

 

[Trevor Wilson]

I want to light up a large tray of ice from within. I was going to throw in
a bunch of 10w halogen bulbs wrapped in blue gel, but then it occurred to me
that 40-50w worth of light might melt a lot of ice.

**PA's idea of a flouro is probably the best, most cost and efficiency
effective, IMO.

Would high-intensity blue LEDs be a better solution - ie, do they have
better efficiency than halogens? Can anyone suggest a suitable source?

**Blue LEDs would convert significantly more power into blue light, than any
incandescent, including halogens. Experiments I've done, suggest that you
could expect at least 200% better power to blue light conversion. The reason
is obvious, of course. Incandescent lamps develop most of their energy in
the infra-red and LF end of the visible spectrum. Halogens do produce a fair
chunk of their power at the blue end, compared to non-halogens, however.
Having said all that, the cost penalty is heavy. I suggest you try one of
the Luxeon emitters. They deliver an impressive amount of light, with a wide
radiation angle and very high efficiency. Although they are significantly
less powerful, the Lumileds are even more impressive (Dollar for Dollar)
IMO.

 

[Sean Coyle]

I have a tendancy to agree with you, the Luxeon Stars or series arranged
emitters would MORE than do the job, they are about 1-5w each, has one
of the highest lumen/watt rating I have ever seen, and they can be
powered by a couple of batteries if need be.

Check out Luxeon.com for further information, Furture Active /
Electronics sells them, they are a little expensive, but are uber x mega
x super bright for their sise, emit no UV and come in 2 kinds of blue as
well as other colours for your application, oh, and did I mention they
are small?

I mean to rival the halogens you'll need heaps. A few luxeon stars
would do the job easily though.

--
Regards,

Sean Coyle
President
Greenroom Networx
Ph: 604.941.7832
Fx: 604.941.7803

"Empowering communities with intuitive, powerful and evolving
communications technology in the 21st century."


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[Arpit]

I looked at those cold-cathode tubes that Jaycar flog for the clueless to
glue to their A-pillars and mud-flaps, but it occurred to me that they use
high-voltage supplies that may not be too compatible with water - although
your clear tubing idea might solve that concern.

Probably the best. Go to www.auspcmarket.com.au or jaycar and get a
blue one, then seal the inverter with silicond, as well as the edges
of the tube. They are about 4 watts, but remember, thats better than
the halogens, cause halogens put out light of all frequencies, and you
are only taking the blue.

 

[Whytech]

I think you'll find the most flexible solution is large diameter fibre
optics. They are available in most countries from specialist suppliers (try
google). Some of these fibres are >1" round and can transmit a lot of light.
You can
a) keep electronics away from water
b) reduce conducted heat from melting the ice
c) cut down on infrared by filtering before entry to the fibre
d) mix colours, intensities etc.

cool eh?
-Andrew


--


Whytech
MSP430 / PIC / AVR tools, SMD prototyping adaptors
Imagecraft MSP430 C compilers
http://www.whytech.com.au

 

[Russ]

I think you'll find the most flexible solution is large diameter fibre
optics. They are available in most countries from specialist suppliers (try
google). Some of these fibres are >1" round and can transmit a lot of light.
You can
a) keep electronics away from water
b) reduce conducted heat from melting the ice
c) cut down on infrared by filtering before entry to the fibre
d) mix colours, intensities etc.

cool eh?

Very true, however there is the issue of time and budget!

I've been experimenting with a 15w halogen bulb, but despite the fact that
the heat generated shouldn't be an issue due to the sheer volume of ice, and
that having water in the tray isn't really a problem, it starts to get
tricky when you consider some risks. If I totally enclose the bulb in a
glass test-tube, it may still get inadvertently shattered, if I encase it in
perspex tube, it may become exposed and without the cooling of water/ice,
the tube will promptly melt (as I discovered). Also, inside glass, if any
water gets in and the unit is exposed, the water will boil and there is a
risk of explosion...

Given the time constraint (next few days) I think I will try a cold-cathode
tube of the Jaycar variety, inside a sealed perspex tube with well-insulated
cabling. That said, even in a few inches of water, it is surprisingly hard
to get a guaranteed watertight seal using silicone.

Thanks for all the suggestions.

Russ.